Patent Literature 1 describes a relay controller for controlling a relay. The relay controller described in Patent Literature 1 includes a resistor and a transistor which are connected in series to a coil of the relay and a diode which is connected in parallel to the resistor and the coil. The relay controller described in Patent Literature 1 applies the initial current to the coil of the relay to turn on the relay. Then, the relay controller described in Patent Literature 1 detects the current flowing through the coil of the relay by using the resistor, and performs PWM (Pulse Width Modulation) control of the transistor so that the detected value is kept at a value lower than the initial current and the relay is kept to be turned on. The PWM control indicates a control repeating to turn on and off a switching element (the transistor, here). On the contrary, a regenerative current flows through the diode. The regenerative current indicates a current which flows through the coil when the switching element is turned off.
Since the relay controller described in Patent Literature 1 can keep the value of the current flowing through the coil of the relay at a value lower than a value of the initial current, the power consumption of the coil of the relay can be reduced.